1. Field of the Invention
The present invention pertains generally to the field of reducing gun barrel erosion for firearms and larger gun-type systems and more particularly to propellant additives to be used for this purpose.
2. Description of the Related Art
Gun barrel erosion has been a problem since the development of gun systems. Due to high flame temperatures created by the propelling charges within gun systems, barrel erosion is inevitable. As propelling charges have been developed that produce greater range and velocities for gun systems, the barrel erosion problem has increased.
Several different methods have been developed to address this problem. First, different barrel designs have been developed to reduce erosion. U.S. Pat. No. 5,712,445 discloses a barrel having cool-burning segments of the barrel stratified with hot-burning segments in order to reduce erosion. A problem associated with such systems is the cost involved in creating such complex systems as well as a decrease in system performance.
Second, many liners or additives have been developed that are deployed within the barrel to reduce erosion. U.S. Pat. No. 5,581,928 discloses an electrically non-conductive lining extending along the length portion of a barrel to reduce erosion. U.S. Pat. No. 3,397,636 discloses a powdery metal-containing inorganic substance that resists erosion placed on the inside of the barrel. U.S. Pat. No. 3,362,328 discloses fibers of polyester, acrylic, silk, wool, glass, and asbestos incorporated into a wax containing calcium sulfate, calcium carbonate, and/or titanium oxide formed into sheets and placed within the barrel to reduce erosion. The problem associated with the above type systems is that reducing the useable area with a gun system decreases performance.
Third, coatings have been developed to apply directly to the propelling charge in order to reduce erosion. U.S. Pat. No. 5,151,557 discloses coating a propelling charge with a composition of sodium or potassium water glass and a volatile flash suppressant of NH4HCO3, (NH4)2CO3, and/or KHCO3. U.S. Pat. No. 4,334,477 discloses using sheets of an additive comprising a mixture of a super water absorbent starch modified polyacrylonitrile which has been subjected to alkaline saponification and water in conjunction with a propelling charge. U.S. Pat. Nos. 3,392,669 and 3,392,670 disclose coating a propelling charge with substances such as feldspar, kaolin, kaolinite, or talc. U.S. SIR HI18 discloses coating a propelling charge with ammonium or potassium carbonates or a bicarbonate. One problem associated with coating propellants is that the coating reduces performance of the propelling charge with minimal erosion gains.
Lastly, new propelling charge compositions have been developed that produce a lower flame temperature, and, thereby, reduce barrel erosion. U.S. Pat. Nos. 3,969,166 and 3,979,236 disclose using a small percentage of a silicate within a propellant charge to reduce the erosive burning of the propellant. However, introducing such materials into a propellant composition have the effect of reducing the performance of the propellant with relatively minor erosion gains.
Therefore, it is desired to provide an additive to a propelling charge composition that greatly reduces gun barrel erosion without significantly reducing the performance of the propelling charge composition.